The easy and rapid spread of bacterial contamination and the risk it poses to human health makes evident the need for analytical methods alternative to conventional time-consuming laboratory-based techniques for bacterial detection. To tackle this demand, biosensors based on isothermal DNA amplification methods have emerged, which avoid the need for thermal cycling, thus facilitating their integration into small and low-cost devices for in situ monitoring. This review focuses on the breakthroughs made on biosensors based on isothermal amplification methods for the detection of bacteria in the field of food safety and environmental monitoring. Optical and electrochemical biosensors based on loop mediated isothermal amplification (LAMP), rolling circle amplification (RCA), recombinase polymerase amplification (RPA), helicase dependent amplification (HDA), strand displacement amplification (SDA), and isothermal strand displacement polymerisation (ISDPR) are described, and an overview of their current advantages and limitations is provided. Although further efforts are required to harness the potential of these emerging analytical techniques, the coalescence of the different isothermal amplification techniques with the wide variety of biosensing detection strategies provides multiple possibilities for the efficient detection of bacteria far beyond the laboratory bench.

Two small Lagocephalus sceleratus juveniles were captured in picarel targeting catches from North Aegean Sea (Greece) in the autumn of 2017. An electrochemical immunosensing tool using magnetic beads as immobilisation support was developed and applied to the rapid 2 screening of tetrodotoxins (TTXs), potent neurotoxins that constitute a food safety hazard when present in seafood. This tool revealed the presence of TTXs in both individuals. Results were compared with those provided by mELISA and LC-HRMS, the latter confirming the presence of TTX. Some of the tissues contained TTX contents close to or above 2 mg/kg. L. sceleratus juveniles had been considered as non-toxic and, to our knowledge, this is the first report of high TTX levels in small L. sceleratus individuals. Such specimens can be mistaken with other edible species, posing a threat to consumers. The availability of low-cost and user-friendly tools for TTXs detection will contribute to guarantee seafood safety.

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ResumoA literatura acadêmica apresenta conceitos que são explorados pelo seu aspecto formal e informal. Também enfatiza que os relacionamentos interpessoais informais complementam e contribuem de forma sinérgica com os relacionamentos formais que ocorrem nas diversas atividades humanas. Alguns autores estudaram a similaridade entre as partes formal e informal, outros indicaram que se poderia estudar os efeitos conjuntos da interação ou o delineamento dos limites da parte informal pela parte formal ou se ambas apresentariam influências recíprocas. Neste trabalho são comparadas as redes sociais formais e informais de duas turmas distintas de alunos universitários e em momentos diferentes para verificar a existência da interação entre os elementos formais e informais dessas redes. Foi realizado um estudo de campo de caráter exploratório com auxílio da análise de redes sociais por meio do software Ucinet 6.0 e Netdraw. Foram coletadas várias medidas com base na percepção dos alunos e a análise dos dados indicou resultados não condizentes com a literatura, indicando a não ocorrência de relação entre os aspectos formal e informal. Dada a importância dessa interação, cabe aos professores e à instituição de ensino prover meios para que isso ocorra. Os resultados indicam a necessidade de mais estudos científicos a respeito do tema.Palavras-chave: análise de redes sociais; redes formais; redes informais; estudante universitário. AbstractThe academic literature presents concepts that are explored by their formal and informal aspects. In addition, it is emphasized that informal interpersonal relationships complement and contribute synergistically with the formal relationships that occur in the various human activities. Some authors have studied the similarity between the formal and informal parts, others have indicated that one could study the joint effects of interaction or the delineation of the boundaries of the informal part by the formal part or if both would have reciprocal influences. In this work we compare the formal and informal social networks of two distinct groups of university students and at different moments to verify the existence of the interaction between the formal and informal elements of these networks. An exploratory field study was carried out with the help of social networks analysis through the software Ucinet 6.0 and Netdraw. Several measures were collected based on the students' perception and the analysis of the data indicated results that were not consistent with the literature, indicating the non-occurrence of a relationship between the formal and informal aspects. Given the importance of this interaction, it is up to the teachers and the educational institution to provide the means for this to occur. The results indicate the need for more scientific studies on the subject.

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The importance of ciguatoxins (CTXs) in seafood safety and their emerging occurrence in locations far away from tropical areas highlight the need for simple and low-cost methods for the sensitive and rapid detection of these potent marine toxins to protect seafood consumers. Herein, an electrochemical immunosensor for the detection of CTXs is presented. A sandwich configuration is proposed, using magnetic beads (MBs) as immobilization supports for two capture antibodies, with their combination facilitating the detection of CTX1B, CTX3C, 54-deoxyCTX1B, and 51-hydroxyCTX3C. PolyHRP-streptavidin is used for the detection of the biotinylated detector antibody. Experimental conditions are first optimized using colorimetry, and these conditions are subsequently used for electrochemical detection on electrode arrays. Limits of detection at the pg/mL level are achieved for CTX1B and 51-hydroxyCTX3C. The applicability of the immunosensor to the analysis of fish samples is demonstrated, attaining detection of CTX1B at contents as low as 0.01 μg/kg and providing results in correlation with those obtained using mouse bioassay (MBA) and cell-based assay (CBA), and confirmed by liquid chromatography coupled to high-resolution mass spectrometry (LC-ESI-HRMS). This user-friendly bioanalytical tool for the rapid detection of CTXs can be used to mitigate ciguatera risk and contribute to the protection of consumer health.

The recent detection of tetrodotoxins (TTXs) in puffer fish and shellfish in Europe highlights the necessity to monitor the levels of TTXs in seafood by rapid, specific, sensitive and reliable methods in order to protect human consumers. A previous immunoassay for TTX detection in puffer fish, based on the use of self-assembled monolayers (SAMs) for the immobilization of TTX on maleimide plates (mELISA), has been modified and adapted to the analysis of oyster and mussel samples. Changing dithiol for cysteamine-based SAMs enabled reductions in the assay time and cost, while maintaining the sensitivity of the assay. The mELISA showed high selectivity for TTX since the antibody did not cross-react with co-occurring paralytic shellfish poisoning (PSP) toxins and no interferences were observed from arginine (Arg). Moreover, TTX-coated maleimide plates stored for 3 months at -20°C and 4°C were stable, thus when pre-prepared, the time to perform the assay is reduced. When analyzing shellfish samples, matrix effects and toxin recovery values strongly depended on the shellfish type and the sample treatment. Blank oyster extracts could be directly analyzed without solid-phase extraction (SPE) clean-up, whereas blank mussel extracts showed strong matrix effects and SPE and subsequent solvent evaporation were required for removal. However, the SPE clean-up and evaporation resulted in toxin loss. Toxin recovery values were taken as correction factors (CFs) and were applied to the quantification of TTX contents in the analysis of naturally-contaminated shellfish samples by mELISA. The lowest effective limits of detection (eLODs) were about 20 and 50µg/kg for oyster extracts without and with SPE clean-up, respectively, and about 30µg/kg for mussel extracts with both protocols, all of them substantially below the eLOD attained in the previous mELISA for puffer fish (230µg/kg). Analysis of naturally-contaminated samples by mELISA and comparison with LC-MS/MS quantifications demonstrated the viability of the approach. This mELISA is a selective and sensitive tool for the rapid detection of TTX in oyster and mussel samples showing promise to be implemented in routine monitoring programs to protect human health.